Sampling

Random Sample:A random sample is where all the members of the target population have an equal chance of being picked. First a list of all the members of the target population is made and all the names are a given number. The sample is then generated using a lottery method e.g. computer randomiser/numbers out of a hat Free from researcher bias Difficult and time consuming Could still end up with a sample that is unrepresentative Seleted participants may refuse to take part

Systematic Sample:A systematic sample is when every 'nth' member of the target population is selected. e.g. every 5th pupil on the school register. A sampling frame is produced which is the list of people in the target population that has been organised e.g. alphabetically. A sampling system is nominated e.g. every 3rd person and the researcher works through the sampling frame until the sample is complete. Free from researcher bias Fairly representative

Stratified Sample:A stratified sample is where the groups that need to be represented in the study are identified and then the sample is taken from those groups. The researcher identifies the different groups that make up the population and the proportions needed for the sample to be representative. The participants are then randomly selected to make up the sample. Free from researcher bias Produces a representative sample making generalisation possible The identified groups cannot reflect all the ways people are different so complete representation is not possible

Opportunity Sample:An opportunity sample is where researchers select anyone who is willing and available at the time of their study e.g. market research Convenient and cheap Unrepresentative of the target population so findings cannot be generalised Lot of researcher bias e.g. not asking people they don't like the look of

Volunteer Sample:A volunteer sample is where participants choose themselves to be part of a study. A researcher may advertise in the newspaper for volunteers Collecting a volunteer sample is easy Asking for volunteers may attract a certain type of person e.g. helpful, keen creating a bias affecting how far findings can be generlised